Water resistant soda base grease



United States Patent 1 2,731,417 WATER RESISTANT SODA BASE GREASE Laurence F. King, Sarnia, Ontario, and Warren C. Pattenden, Courtright, Ontario, Canada, assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application March 31, 1953, Serial No. 346,012

8 Claims. (Cl. 252-421) The present invention relates to a water resistant lubricating grease and particularly to a grease thickened with an alkali metal soap, especially a sodium soap. The invention applies to greases which are normally subject to water leaching and involves improvement both in their water resistance and in oxidation resistance by addition of a modifier.

In the prior art numerous types of lubricating greases have been disclosed, one of the most common of which is a so-called soda base grease. Soda base greases ordinarily consist primarily of a major proportion of a lubricating oil, usually but not always a mineral base oil, thickened to a solid gel or grease-like structure by addition of suitable quantities, usually between about and 40% by weight, of soda soaps of higher fatty acids. Conventional soda base greases containing 5 to 30% or more of soda soap of C12 to C24 fatty acids are widely used as lubricants because of their good structural characteristics. Mixed base greases are made also, including soda soaps plus other soaps. In general the greases which contain appreciable quantities of soda soaps are satisfactory in grease texture at reasonably high operating temperatures. They do not break down by separation of oil from the soap, they do not readily become grainy, and

they are relatively inexpensive products. They have one serious deficiency for many uses, however, in that they are quite subject to Water leaching or to structural breakdown and other types of deterioration in the presence of liquid water or other moisture. Moreover, known materials used for waterproofing in general are not efiective.

This deficiency is due primarily to the fact that most soda soaps of conventional fatty acids are highly watersoluble. When greases containing such soaps come into contact with substantial quantities of water or moisture the soap is gradually leached out of the grease. Eventually the oil is left without an effective thickener. The oil runs out of the bearing or away from other mechanical parts to be lubricated, leaving them unprotected. Lubrication failure results in many cases.

Another deficiency of soda soap greases, and most other lubricating greases, is their tendency to oxidize in the presence of air. The lubricating oils in the grease themselves deteriorate in the presence of air, especially under prolonged high temperature conditions, and the soaps also are degraded per se. Eventually the greases become crusted and hard and lose their lubricating value.

According to the present invention it has been dis covered that soda base greases in particular and other greases containing soda or other water soluble soaps in general can be improved in both their water sensitivity 'and in their oxidation resistance by adding thereto relatively small proportions of alkali metal siliconates. Siliconate proportions from as little as 0.1 to as much as by weight, based on the weight of the total grease composition, may be used. The preferred range is be tween 0.5, and 5% of siliconate.

A particularly useful type ofsiliconate is one sold commercially by the General Electric Company as SC- 50. This product is an alkaline salt, ordinarily sold in aqueous solution, containing minor proportions of basic salts such as NazO and a major proportion of silicon-con- 2,731,417 Patented Jan. 17, 1956 ice taining salts such as sodium methyl siliconate, the siliconate radical being understood to have the approximate average formula CH3Si01.5. This material as sold commercially has a specific gravity of about: 1.23 and a pH value of about 13.

These siliconates may be prepared from basic chlorosilanes by treatment with alkali according to known methods of the prior art. The greases to which they are added are prepared preferably by forming a combination of the siliconate salt with the ordinary soap, e. g. sodium soap of C12 to C24 fatty acids, used for thickening the grease. This combination is then dispersed in a suitable lubricating oil. The resulting grease product has not only a much greater water resistance than conventional soda soap greases but its oxidation resistance likewise is improved very appreciably. The use of a single modifier to accomplish these results is very advantageous.

Inasmuch as the siliconate has a high degree of alkalinity (pH of about 13) it can be used as part or all of the saponifying agent in the preparation of soap from fatty acids, if desired. In dilute solutions sodium methyl siliconate appears to exist largely or approximately in the monomeric form CH3Si(OH)zONa. When dried it loses water and forms a polymer of approximate formula (CHzSiOzNah.

In concentrated solutions many different polymers probably exist such as the dimer and other low polymers. By adding additional alkali (NaOH) to such solutions polybasic compounds of the ortho acid may be formed such as CH3Si(ONa)s. When these sodium salts are used to saponify fatty acids, the alkali is neutralized. A more general formula for these salts is CHSSlOxMy where x and y are integers of l to about 5 and. M is an alkali metal.

Methyl siliconic acid, CH3Si(OH)3, is liberated when acids are added to aqueous solutions of the sodium salts described above. Even very weak acids, such as the carbon dioxide present in the atmosphere, can bring about this reaction. The free methyl siliconic acid is insoluble in water and precipitates out in situ on the soap that is formed. This appears to be the actual basis for the water-proofing action of sodium methyl siliconate in soda base greases and the like. At room temperatures the curing process necessary to effect waterproofing in the air, using no other curing medium, requires about 24 hours. At elevated temperatures such as 300 F. or so, which is a common grease cooking range, a time of 15 to 60 seconds is sufiicient.

The invention may be shown more clearly by reference to results obtained with several experimental sodium base greases of the formulas shown in the table below. These were compared with a conventional commercial sodium stearate grease designated A. Grease B was prepared by adding an aqueous solution containing 1.5% by weight, based on the treated grease, of sodium methyl siliconate (General Electric -50) to the soap. Thereafter the soap-salt combination was dehydrated at 300 F. The dehydrated soap combination was prepared by cooking. in asmall quantity of mineral base lubricating oil. Later the soap concentrate thus formed was cut back to the desired consistency with further quantities of mineral base lubricating oil.

In grease C a much larger amount, 10%, on a dry basis, of sodium methyl siliconate was incorporated in the grease, omitting sodium hydroxide altogether. The alkali of the siliconate served as the entire saponifying ingredient for converting thefatty acids tio soap.

It will beobserved in the table below that the water resistance of the new greases B and C was very good for a short period of time even at temperatures as high as the boiling point of water. Ordinary soda soap greases are somewhat water resistant up to about F., this viscosity indexes.

figure applying to sodium stearate greases. As far as the inventors are aware, no prior art soda soap grease has been prepared hitherto with an appreciable water resistance above this temperature. In fact it is very difficult to water-proof a soda base grease. Addition of alkyd resins, for example, which are effective waterproofing materials for certain other types of greases which are moisture sensitive, are totally ineffective in soda base greases.

The extraordinary leaching resistance of greases B and C shown in the table below at 150 F. is considered remarkable. This probably simultates conditions actually encountered in lubricating service, for example, in electric motors, automobile wheel bearings, and the like. It will be noted that in a special test at 150 F., running a ball bearing wet for one hour, at 600 R. P. M. the new greases lost only 2 to of their weight due to leaching. The conventionfl prior art soda soap grease lost over 99%.

Table I out in these synthetic oils, especially the esters, without hydrolysis or other degradation. Hence, it is usually preferred to perform the saponification step in the presence of mineral oil if the soaps are to be formed in situ. The fatty acids used for the soap may include substituted acids such as hydroxy stearic acid, keto acids, etc.

Obviously, conventional modifiers such as metal deactivators, corrosion inhibitors, tackiness agents, viscosity index improvers and supplementary corrosion inhibitors may be used in conventional proportions without departing from the spirit or purpose of the invention.

What is claimed is:

1. A lubricating grease composition prepared by thickening a major proportion of lubricating oil with a sodium soap of a high molecular weight fatty acid, admixing 0.1 to by weight, based on the total composition, of sodium methyl siliconate of approximate formula CH3Si(OH)2ONa in the presence of Water, and heating the grease to a dehydrating temperature.

Formulae and inspections of sodium soap greases Formula, percent by Wt.:

Stearlc Acid Sodium Hydroxide (dry basis) Sodium Methyl Siliconate (dry basis) Mineral 8000, V./100 SUS=675,

V. I. Mineral Oil, V./100 SUS=320,

Inspections:

Free Alkali, percent Mi cronenetration. AS'IM Wkd. penetration (calc Water Resistance Tests, 8 GP(),

Method9.2.

295 water turns cloudy;

g r e a s e disintegrate.

grates giving some free 011.

Leaching Beslstance-VVL- Amendment 1, Method At l F., Grease Loss, percent. At 150 F., Grease Loss, percent.

water turns 6161155,? does not disinteno cloudiness in water.

.. 1 Phenol treated Tia Juana distillate.

1 Acid and clay treated Tia Juana distillate. 1 Method designed to test tendency of grease to emulsity when in contact with water; 0.5-1 gm.

grease on the end of a stirring rod is immersed in 200 cc. boiling water for ten seconds.

4 3 gm. grease is packed into 204K type ball hearing which is rotated at 600 R. P. M.

Water is pumped through a 1 mm. capillary tube at 5 cc./sec. and impinges on the cnd'plate of the hearing V4 inch above the outer o ening of the bearing housing. perature specified usually is 120 F. These tests, however, as indicated.

It may be noted, as indicated above, that the oxidationresistance was very markedly improved. A grease hardening test, which is a good measure of oxidation, was devised so that a micropenetration or hardness measurement of 5 was established as the limit of useful grease life in a 300 F. oxidation test. Grease A, a conventional anti-friction bearing grease without the sili-' conate, showed a life in this test of only 290 hours at 300 F. Grease B showed a life of 810 hours at the same temperature. p

Another grease, containing 20% sodium stearate in a lubricating oil of 500 S. S. U. viscosity, which may be considered essentially a blank for grease B, showed a test life of only 300 hours. When 1% of one of the best known conventional oxidation inhibitors, phenyl alpha naphthylamine, was added the oxidation life became 690 hours. The latter, of course, has no waterproofing value.

While most greases utilize mineral base oils of between about 100 and 2000 S. S. U. viscosity, and viscosity index between 40 and 100 or so, special purpose lubricants may include more viscous oils and/or oils of higher Also, synthetic oils may be used in whole or in par as will be readily understood by those skilled in the art. Thus, synthetic esters, glycols, polyglycols and related ethers, acetals, and the like may be used to replace part or all of the mineral base oil constituent. It should be kept in mind, however, that saponification reactions with strong bases usually cannot be carried The duration of test is one hour.

were carried out at higher temperatures The tem- 2. Composition as in claim 1 wherein the amount of siliconate is 0.5 to 5%.

3. Composition as in claim 1 wherein the lubricating oil is a mineral base oil of to 2000 S. S. U. viscosity at 100 F. V

4. Composition as in claim 1 wherein the siliconate is used as the 'saponifying agent for at least a portion of the fatty acids.

5. The process of making a lubricating grease which comprises mixing a lubricating oil with a grease-forming proportion of a composite of soda soap and sodium methyl siliconate, in the presence of Water, and heating the mixture to a dehydrating temperature.

' 6. The process of claim 5 wherein the lubricating oil is a mineral base oil of 100-2,000 S. S. U. viscosity.

7. The process of making a lubricating grease which comprises preparing a soda soap by saponifying fatty acid of the C1z-C22 range in a mineral base lubricating oil in the presence of about 01-10% by weight, based on total grease, of sodium methyl siliconate of approximate formula CH3Si(OH)2ONa.

8. A lubricating grease composition prepared by dispersing in a lubricating oil under grease-making conditions a grease-making proportion of a sodium soap of a high molecular weight fatty acid and adding thereto about 01-10% by weight, based on the total composition, of sodium methyl siliconate of approximate formula CHaSi(0H)zONa.

No references cited. 

1. A LUBRICATING GREASE COMPOSITION PREPARED BY THICKENING A MAJOR PROPORTION OF LUBRICATING OIL WITH A SODIUM SOAP OF A HIGH MOLECULAR WEIGHT FATTY ACID, ADMIXING 0.1 TO 10% BY WEIGHT, BASED ON THE TOTAL COMPONSITION, OF SODIUM METHYL SILICONATE OF APPROXIMATE FORMULA CH3SI(OH)2ONA IN THE PRESENCE OF WATER, AND HEATING THE GREASE TO A DEHYDRATING TEMPERATURE. 